With popularity of smart devices, an increasing number of devices are equipped with a camera function. Generally, a single-lens camera is disposed on a rear surface of a device, or another single-lens camera is also disposed on a front surface of the device.
A common camera function includes a preview image function, that is, an image currently acquired by a lens is dynamically displayed on a built-in display of the device or on an external display. For example, when a user is relatively satisfied with a current preview image, the user may press a particular button, for example, a hardware button disposed on the device or a button simulated on a camera application, so as to provide a photographing operation instruction to the device. When the photographing operation instruction is received, the device performs processing on the current preview image and generates a picture.
To improve photographing quality, a conventional single-lens camera may identify a scenario. For example, when a night scene or a backlit scene is detected by using a scenario identification algorithm, the single-lens camera may implement an increase in brightness by prolonging an exposure time or improving film speed, so as to improve a photographing effect. However, after brightness in a night scene or a backlit scene is increased by the single-lens camera, picture flickering on the preview image is likely to be caused. Specifically, after the single-lens camera acquires a new preview image according to a parameter that is obtained after brightness is increased, the single-lens camera determines, according to the new preview image, whether a current photographing environment is still a night scene or a backlit scene. In this case, because brightness of the preview image has already been increased, and the single-lens camera may determine that the current photographing environment is no longer a night scene or a backlit scene, a photographing parameter is restored to a normal value, that is, brightness is decreased; therefore, a next-frame preview image darkens again. Repeated increases and decreases of brightness cause picture flickering on the preview picture.